In the field of chemical industry, metallurgy and environment, some complex multiphase flow processes are often involved in which there are one or two or more dispersed phases. It is urgent to solve the problem on the measurement of concentration and size distribution of dispersed phase particles in such a multiphase reactor.
At present, various probe methods are most commonly used based on optical fiber reflex or conductance (capacitance). Both methods have been applied successfully in the study of gas-liquid and liquid-solid systems, for example, the monofilament capacitance probe measurement system of phase containing rate and phase interface in multiphase pipe flow (CN 1865966A) and the measurement method and device of the two-phase flow parameter based on the double capacitance probe (CN 101413911A). However, both of them have some limits. Multiphase flow to be measured should be conductive for the conductance probe, while the fiber optic probe is very easy to be broken. Signals will interfere with each other when there are two or more dispersed phases. Sampling method is simple in principle and convenient in operation and can simultaneously measure the concentration and size distribution of dispersed particles. However, it is difficult to achieve the equivariant momentum condition needed for an accurate sampling measurement. At the same time, because it is an offline measurement, it is not applicable to non-steady processes. Particle size analyzer is used to measure solid particle size and its distribution and divided into settlement-type particle size analyzer, sedimentation balance, laser particle size analyzer, optical particle counter, resistance type particle counter and particle image analyzer etc. according to different measuring principles. In the process using a variety of particle size analyzer, it is often required to carry out the tedious sample preparation, so the particle size measuring method is not a real online measuring method.
Optical photography is the most intuitive measuring method. The outstanding advantage of non-intrusive photography is that it does not interfere with the flow field. And its shortcomings are that the measured reactors must be transparent or installed with viewports, and the holdup of bubbles or solid particles must be lower. Invasive photography such as optical fiber endoscope can be directly inserted into the reactor for online measurement. But the measurement accuracy is limited by the fiber diameter. At the same time, the wide-angle lens installed at the front end of the endoscope will cause a larger image distortion.